This invention relates to turbo machinery power cycles, and, more particularly, to turbine inlet fogging and turbine combustor steam injection.
It is known that water or steam may be injected into a gas turbine at various points within a cycle to increase the mass flow of motive fluid to augment gas turbine power, and/or to control NOx emissions. Specifically, steam injection into the combustor, and compressor air inlet fogging both produce increased output, and improved heat rate when gas turbine exhaust energy is used for steam generation. Current state of the art systems for steam injection and inlet fogging, however, require a demineralized water treatment facility to produce steam suitable for introduction into the gas turbine.
The present invention provides a cycle design method for gas turbine power plants that includes both steam injection and inlet fogging. The system design described in this disclosure is unique in that it does not require a demineralized water treatment facility that is typically required for current state of the art systems. Rather, steam is produced in this system by flashing high pressure hot water streams to a flash tank/dearator (or simply, flash tank) operating at reduced pressure, while the water quality in the tank is controlled with blowdown. Specifically, makeup water is heated using gas turbine exhaust energy in a waste heat recovery unit and then flashed via a first stream to the flash tank operating at a lower pressure, which results in the production of saturated steam and water. Saturator bottoms water from the flash tank is pumped to a higher pressure, and then heated in the waste heat recovery unit using the exhaust energy from the gas turbine. The saturator bottoms water leaving the waste heat recovery unit is then flashed via a second stream to the flash tank, also resulting in the production of saturated steam and water. The liquid remaining after flashing the first stream, is dearated with the steam produced by flashing the second stream in the flash tank. The resultant bottoms water stream draining from the tank is thus dearated, allowing for economic material selection for the system.
A small portion of the steam produced in the flash tank is condensed in a heat exchanger (in heat exchange with the makeup water stream), and the resulting water is of acceptable quality (dissolved solids and salts acceptable) for inlet fogging. The remaining steam produced in the flash tank is heated in the waste heat recovery unit and is subsequently injected into the gas turbine combustor.
The makeup water for this system may be potable water with minimal water treatment, i.e., no demineralization is required. This is possible due to the use of the flash tank/dearator for steam production, and the control of contaminants concentration in the flash tank.
Accordingly, in one aspect, the invention relates to a gas turbine power plant that includes a compressor, a combustor and a turbine, and that also includes compressor inlet fogging and combustor steam injection. The invention specifically relates to an arrangement for supplying water for inlet fogging and steam injection without demineralization treatment comprising a flash tank arranged to receive heated potable water and to separate the heated potable water into saturated steam and water; a blowdown stream for controlling contaminants in the water within the flash tank; one or more conduits arranged to supply a first portion of the saturated steam in the flash tank to the combustor; one or more conduits arranged to supply a second portion of the saturated steam to a heat exchanger where the saturated steam is condensed; and one or more conduits for supplying condensed saturated steam to an inlet fogger in fluid communication with the compressor.
In another aspect, the invention relates to a steam injection and inlet fogging system for a gas turbine power plant comprising a gas turbine having a compressor, a combustor and a turbine for driving a generator; a waste heat recovery unit arranged to receive exhaust gas from the turbine, the waste heat recovery unit having a plurality of heat exchange sections for heating water with the exhaust gas; a flash tank for producing steam arranged to receive heated water from the waste heat recovery unit; means for flashing a first stream of water from a first of the plurality of heat exchange sections to the flash tank to thereby produce saturated steam and water at a first location in the flash tank; means for flashing a second stream of water from a second of the plurality of heat exchange sections to the flash tank to thereby produce saturated steam and water at a second location in the flash tank; means for supplying a portion of the saturated steam produced in the flash tank to the gas turbine combustor; means for supplying a remaining portion of the saturated steam to the compressor via an inlet fogger; and means for controlling contaminants in the water produced in the flash tank.
In still another aspect, the invention relates to a method of providing steam for a steam injection and inlet fogging system for a gas turbine power plant that includes a gas turbine having a compressor, a combustor and a turbine for driving a generator, and without having to provide a demineralization treatment for water used to generate the steam comprising:
a) supplying a heated makeup water in a first stream to a flash tank for producing saturated steam and water;
b) draining water from the flash tank while removing contaminants therefrom and, after heating, recirculating a portion of the drained water to the flash tank in a second stream;
c) removing saturated steam from the flash tank/dearator and supplying a portion of the saturated steam to the combustor and another portion of the saturated steam to the compressor via an inlet fogger.